In the practice of determining blood glucose, known photometric measuring systems are based on irreversibly reacting carrier-bound test elements in the form of test strips or test tapes. These are intended to enable also the layperson to measure blood glucose by means of processing in automated compact hand-held devices, outside of a laboratory environment, with sufficient precision as required in the medical treatment of diabetes. The measuring process provides that, after the application of a blood sample, the analyte concentration is determined by means of appropriately repeated photometric measurements. For this, it is important that changes in the boundary conditions of the measurement are detected independently of the actual detection of the analyte.